PRESBYOPIC TREATMENTS

Presbyopic LASIK and intracorneal hydrogel implants are both viable options for providing some degree of near vision but both types of approach suffer from the same drawback of a reduction in distance vision in the treated eye, Günther Grabner MD, University Eye Clinic, Paracelsus Medical University, Salzburg, Austria, told a session of the XXIX Congress of the ESCRS.

Dr Grabner noted that the corneal approaches to presbyopia have their pros and cons. For example, presbyopic LASIK has been the subject of clinical research since the late 1980s and in its current forms appears to offer a reversible or at least partially reversible bifocality. On the other hand, it can only provide a limited amount of near vision and there is as yet no consensus as to which of the many available techniques is best.

Corneal inlays, meanwhile, offer a somewhat more reversible means of extending the range of vision in presbyopic patients. However, like presbyopic LASIK, the models currently in use also provide a fairly limited range of near and/or intermediate vision. Moreover, they have been the subject of little in the way of peer-reviewed published research and there is even less information about their longer term safety and efficacy, he said.

Different LASIK approaches

Dr Grabner said that there are four main types of presbyopic LASIK ablation profiles. They are the central steep island, the decentred steep island, and the centred steep annulus, and a global optimum, which is a hyperprolate shape optimised for asphericity and radius of curvature.

He noted that a ray tracing computer simulated analysis of those approaches by Tobias Koller MD and Theo Seiler MD, PhD in Zurich, Switzerland showed that the global optimum approach and central steep island approaches were the most promising. The decentred steep island and centred steep annulus produced significantly worse results in terms of both near and distance vision (Koller et al, J Cat Refract Surg; 32: 2118-2123).

“You should probably not use the techniques like the decentred steep island or centred steep annulus ablations, they have some theoretical problems. The techniques with a central zone for near vision with the pupil acting as the driving force, like the Schwind Presbymax and the AMO/VISX CustomVue, are probably the ones you should consider if you are going to try this technique,†Dr Grabner said.

In a study by Bruce Jackson MD and associates in Ottawa Canada involving 19 eyes that underwent a custom presbyopic ablation with the CustomVue system, the aspheric ablation with the centre optimised for near vision resulted in close to 70 per cent achieving J1 and more than 90 per cent achieving J3 or better in bilateral binocular near visual acuity.

“Bilateral presbyopic LASIK treatments show the best results. If you know how to do it well, the patients are quite satisfied and about 50 per cent will be completely spectacle-free. You have to expect a loss of one or two lines of best spectacle-corrected distance visual acuity, which is quite a loss. And over time, near vision deteriorates and far vision improves a little bit. Distance vision is not as good in myopes as it is in hyperopes,†Dr Grabner added.

The return of corneal inlays

Corneal inlays are lenticules designed to be placed beneath a flap similar to that used in LASIK procedures. They include inlays designed to improve the near focus of the nondominant eye through multifocal optics of the lenticule itself, as in the case of the Flexivue (BioVision), those that provide a near add through an increase in curvature in the central cornea, like the newest version of the Vue+ inlay, or Presbylens (ReVision Optics) as it is now called, and those, like the Kamra inlay (AcuFocus), which is based on the concept of the pinhole lens.

Dr Grabner noted that the published peer-reviewed data regarding the inlays is very scarce. The most he could find regarding the Flexivue microlens, was an abstract of a study conducted by Ioannis Pallikaris MD in Crete, involving 45 patients, but he expects detailed publications soon. It showed that patients’ mean uncorrected near and distance visual acuity in their treated eye was 0.6. There was also in increase in higher order aberrations.

Regarding the Vue+ lens, Enrique Barragan MD, Monterrey, Mexico, reported his findings in 17 patients with the inlay at the 2010 XXVIII Congress of the ESCRS in Paris. The study showed that at nine months’ follow-up patients gained an average of four lines of uncorrected near visual acuity. However, the uncorrected distance visual acuity in the treated eye was 20/20 or better in fewer than 20 per cent of patients, compared to over 90 per cent of patients before the surgery.

The Kamra inlay is currently the best researched. It is currently the only inlay for which the results appear to have been published in peer-reviewed journals. In addition, more than 8,000 of the inlays have been implanted worldwide, including more than 4,000 of the inlays implanted by Minoru Tomita MD in Japan in conjunction with LASIK procedures.

Moreover, in a recently published study involving 32 patients in whom Dr Grabner and his associates implanted the inlay as part of an international FDA trial, eyes receiving the inlay had a mean gain of 4.6 lines of uncorrected near visual acuity, 98 per cent of patients in the study achieved J3 or better and half achieved J1at 36 months follow-up. In addition they only lost a mean of 0.8 lines of uncorrected distance visual acuity significantly better than any other technique..

“There are some excellent corneal options for presbyopia and in patients with a clear lens, I don’t think you have to go into the eye with all the risks involved,†Dr Grabner concluded.